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Swift observations of the 2006 outburst of the recurrent nova RS Ophiuchi. I. Early X-ray emission from the shocked ejecta and red giant wind

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posted on 24.10.2012, 09:06 by MF Bode, TJ O'Brien, JP Osborne, KL Page, F Senziani, GK Skinner, S Starrfield, J-U Ness, JJ Drake, G Schwarz, AP Beardmore, MJ Darnley, SPS Eyres, A Evans, N Gehrels, MR Goad, P Jean, J Krautter, G Novara
RS Ophiuchi began its latest outburst on 2006 February 12. Previous outbursts have indicated that high-velocity ejecta interact with a preexisting red giant wind, setting up shock systems analogous to those seen in supernova remnants. However, in the previous outburst in 1985, X-ray observations did not commence until 55 days after the initial explosion. Here we report on Swift observations covering the first month of the 2006 outburst with the Burst Alert Telescope (BAT) and X-Ray Telescope (XRT) instruments. RS Oph was clearly detected in the BAT 14-25 keV band from t = 0 to t ~ 6 days. XRT observations from 0.3 to 10 keV started 3.17 days after outburst. The rapidly evolving XRT spectra clearly show the presence of both line and continuum emission, which can be fitted by thermal emission from hot gas whose characteristic temperature, overlying absorbing column (NH)W, and resulting unabsorbed total flux decline monotonically after the first few days. Derived shock velocities are in good agreement with those found from observations at other wavelengths. Similarly, (NH)W is in accord with that expected from the red giant wind ahead of the forward shock. We confirm the basic models of the 1985 outburst and conclude that standard phase I remnant evolution terminated by t ~ 6 days and the remnant then rapidly evolved to display behavior characteristic of phase III. Around t = 26 days, however, a new, luminous, and highly variable soft X-ray source began to appear, whose origin will be explored in a subsequent paper.

History

Citation

Astrophysical Journal, 2006, 652 (1), pp. 629-635

Version

VoR (Version of Record)

Published in

Astrophysical Journal

Publisher

American Astronomical Society, IOP Publishing

issn

0004-637X

Copyright date

2006

Available date

24/10/2012

Publisher version

https://iopscience.iop.org/article/10.1086/507980

Language

English